Pharmacokinetics Study Of Iloperidone In Human

Objective: An assay on Chinese population was undertaken to investigate the pharmacokinetics of iloperidone. This assay is to explore the effect of gene polymorphism on pharmacokinetics. The goal is to provide a theoretical basis for the adjustment of clinical regimen and individualized dosing.Methods:(1) To establish a LC-MS/MS method for the determination of ILP and its two metabolites(P88 and P95) in human plasma at the same time. The separation was performed on the Agilent C8 colunm(4.6×100 mm, 3.5 μm), and the mobile phase was acetonitrile: 2 mmol·L-1 ammonium formate containing 1.5% formic acid( 28:72) with a flow rate of 600 μL·min-1, Electrospray ionization(ESI) source was applied and operated under multiple reaction monitoring(MRM) mode using the transitions of m/z 427.2â†'233.2, 429.2â†'261.2, 429.2â†'233.2 and 430.2â†'233.1 for ILP, P88, P95 and ILP-D3 respectively. Plasma samples were extracted by acetonitrile and analyzed by LC-MS/MS.(2) To study the pharmacokinetics of ILP in healthy Chinese volunteers, 20 healthy subjects were randomly picked from volunteers and divided into two groups(Sex ratio was not less than 1: 3). One group was administered to take a single dose of iloperidone tablet 1mg(one tablet), and the other group took a single does of 2mg(two tablets). Blood samples(4 m L) were collected at pre-dose(0 h) and at 0.5, 1, 1.5, 2.0, 3.0, 4.0, 5.0, 6.0, 8.0, 10, 12, 14, 24, 36, 48, 72, 96 and 120 h post-dosing. Plasma was separated by centrifuged immediately at 4000 rpm, 4 ℃×10 min and stored at temperature of- 30℃ until analysis. The plasma drug concentrations of ILP, P88 and P95 were measured by HPLC-MS/MS, and the pharmacokinetic parameters were analyzed using SPASS 17.0. Considering the tolerance of healthy subjects, multiple-dose pharmacokinetic studies were not designed.(3) To study the pharmacokinetics of iloperidone on patients with schizophrenia, 31 patients were enrolled in this study. Starting from taking the small dose, those 30 patients were administrated to take gradually increased tolerable effective dose and maintained to take the effective dose for one week. The maintenance therapy doses were developed as 6,8,10 and 12 mg per dose, twice per day, and pharmacokinetic studies were conducted on the last day. Blood samples(4 m L) were collected at pre-day, pre-dose(0 h) and at 1.0, 2.0, 3.0, 4.0, 6.0, 8.0, 12, 24, 36, 48 h post-dosing. Plasma was separated by centrifuged immediately at 4000 rpm,4 ℃×10 min and stored in-30℃ environment until analysis. The concentrations of ILP, P88 and P95 in plasma were measured by HPLC-MS/MS, and the pharmacokinetic parameters were analyzed by SPASS 17.0.(4) Before the assay, the gene blood were collected to classify the CYP2D6(1228G>A),(1457G>C)and(1470T>C)gene types of 51 subjects, including 20 healthy volunteers and 31 patients, by using PCR method. How different gene types could influence the pharmacokinetics of ilperidone was analyzed using SPASS 17.0.Results:(1) The method is sensitive, accurate, and reproducible. Endogenous substances did not interfere with the measurement of the analytes and the internal standard. The method was validated over the concentration range of 0.01~15 ng·m L-1 for ILP and P88, and 0.02~20 ng·m L-1 for P95, respectively. The intra- and inter-day precisions were within the acceptable range, and the means of the extraction recovery were more than 75%. Plasma samples were stable at room temperature for 8 h,-30℃ repeated freezing and thawing three times and frozen under-30℃ for 89 days.(2) The pharmacokinetic parameters of ILP, P88 and P95 after a single-dose of 1mg, 2mg on healthy subjects had no significant difference between doses, except MRT of ILP, P88 and P95. Compared to the healthy subjects, there were significant differences on the pharmacokinetic parameters such as CL and Vd after a multiple-dose of 8mg, 10 mg, 12 mg in patients. Qver the dose of 1mg-2mg and 8mg-12 mg, the Cmax and AUC were related with dose, but not very well over the dose of 8mg-12 mg. Qver the low dose range, the AUC of ILP of female subjects were significantly higher than male subjects, CL of ILP of female subjects were significantly lower than male subjects, while over the high dose range, there was no significant different between sexs in the pharmacokinetic parameters.(3)All the subjects were classified by three genes, among which only 1228G>A was related to the metabolism of iloperidone. The AUC0-∞, t1/2 and CL of the parent had significant differences between the mutant and wild-type. The AUC0-∞ and t1/2 of mutant were shorter than the wild-type’s, while the CL was higher. Besides, the exposure of P95 in the mutant group was higher than the wild-type’s. It means that the mutant of 1228G>A increased the activity level of CYP2D6, and enhanced the mentabolish of iloperidone.Conclusion: Qver the dose of 1mg-2mg and 8mg-12 mg, the Cmax and AUC were related with dose, but not very well over the dose of 8mg-12 mg. There was a significant difference in CL and Vd after a multiple-dose in patients compared to the healthy subjects, probably due to the differences of physiological functions and drug combinations among the patients. The mutation of CYP2D6(1228G>A) gene had significant impacts on the process of iloperidone in vivo. It increased the activity level of CYP2D6 and enhanced the mentabolism of iloperidone, therefore increased the exposure of P95. It was suggested that the individual differences should be taken into account in the plans of administrations.